Conventional apparatus for tightening up a bolt B having at its forward end a tip T which is to be sheared includes an inner socket 200 engageable with the bolt tip T and an outer socket 180 engageable with a nut N (FIG. 8). The two sockets are coupled to an epicyclic train and thereby subjected to the reaction of rotation to tighen up the bolt B and shear the tip T at a circumferential groove C of the bolt B. The tip remaining in the inner socket 200 is knocked out by an ejector pin 240 disposed in the inner socket.
The ejector pin extends rearward through the sun gear of the epicyclic train and has a rear end in engagement with a discharging lever. The ejector pin is retained in a retracted position or allowed to advance when released by manipulating the lever.
However, when the ejector pin is as long as the entire length of the tightening apparatus as in the conventional apparatus, the following problem is encountered.
To give an increased force of inertia when projected, the ejector pin 240 has a thick front end portion 240a. Because the junction between the thick portion 240a and the other slender portion 240b is prone to cracking due to the impact of projection, there arises a need to replace the ejector pin. Nevertheless, the ejector pin, extending through the epicyclic train, is not removable easily but requires a cumbersome procedure for replacement.